Atari 800XL Service Manual

SECTION
I
THEORY
OF
OPERATION
The
Atari
800XL
W
Is
an
enhanced
version
of the
existing
ATARI
Computer
Systems.
It
can
be
used
with
any
of
the
existing
Atari
peripheral
devices
used
with
the
400’V600XL"V800
,M
/ 1
20QXL
M
Computers.
The
printed
circuit
board
contains
64K
of RAM
,
an
operating
systems
that
contains
ore 1
6K X 8
ROM
and
an
on-
board
Atari
BASIC
programming
language
I.C.
The
console
contains
the
keyboard
and
four
function
keys
(
including
a HELP
key),
plus
a
RESET
key,
a
detachable
( RF)
TV
interface
cable,
connector
Jack
for
daisy-chaining
peripherals
and
connecting
hand
controllers,
a
single
cartridge
slot,
ore
status
LED
(POWER),
a5 pin
DIN
Monitor
Jack,
and
a
parallel
bus
interface
USER INTERFACE
The
Atari
800XL
is
a
general
purpose
microcomputer
that
uses
a
6502C
microprocessor.
The
800XL
console
is
the
central
processing
unit
for
its
respective
system.
The
right
side
panel
contains
the
controller
jacks
that
accept
the
Atari
X-Y
joysticks
and
paddle
controllers.
The
rear
panel
contains
the
serial
input/output
(SIO)
jack,
the
parallel
bus
interface,
theRF
jack,
the
monitor
jack,
the
channel
2-3
switch,
the
power
in
jack,
and
the
power
switch
(On/Off).
The
console
has
a 3/4
stroke,
56
key,
alphanumeric
keyboard,
that
includes
special
characters
and
controls,
space
bar,
four
function
keys,
HELP
key,
and
power
indicator.
The
function
and
HELP
keys
are
discussed
below.
FUNCTION KEYS
HELP
-
Returns
to
main
self-test
menu
from
individual
test
and
for
future
software
development
for
user
“help"
functions.
If
you
are
familiar
with
I200XL
operation,
this
kev
do&
noi
function
the
same.
OPTION
-
Allows
the
player
to
choose
variations
of
a
program.
If
the
OPTION
Key
is
not
depressed
and
held
at
the
time
the
computer
is
turned
ON,
the
built-in
BASIC
is
automatically
enabled.
If
the
OPTION
key
is
depressed
and
held
at the
same
time
the
computer
is
turned
ON,
the
on
board
BASIC
is
disabled
and,
when
there
is
no
cartridge
or
diskette
in
the
system,’
the
5

Atari 800XL Specifications

General

Manufacturer	Atari
Type	Home computer
Release year	1983
CPU	MOS Technology 6502C
RAM	64 KB
ROM	24 KB
Operating System	Atari OS
CPU Speed	1.79 MHz (NTSC) / 1.77 MHz (PAL)
Graphics	ANTIC and GTIA chips
Display resolution	160×192 to 320×192 pixels
Sound	POKEY chip
Storage	Cassette tape, floppy disk
Ports	Serial, parallel, monitor, joystick ports